Two-temperature refrigerating apparatus



C. H. WURTZ ETAL TWO-TEMPERATURE REFRIGERATING APPARATUS 11 Shets-Sheet l T 1111 LTE- March 16, 1954 Filed April 28, 1951 C. H. WURTZ ET AL TWO-TEMPERATURE REFRIGERATING APPARATUS Filed April 28, 1951 March 16, 1954 11 Sheets-Sheet 2 INVENTOR. C l W- B-Y W' MW 5%/ March 16, 1954 c. H. wURTz ET AL Two-TEMPERATURE REFRIGERATING APPARATUS l1 Sheets-Sheet 5 Filed April 28. 1951 March 16, 1954 C. H. WURTZ ET AL TWO-TEMPERATURE REFRIGERATING APPARATUS 1l Sheets-Sheet 4 Filed April 28, 1951 Mmh 16, 1954 c. H. WURTZ ET AL 2,672,020

TWO-TEMPERATURE REFRIGERATING APPARATUS Filed April 28, 1951 ll Sheets-Sheet 5 PPs-L1 IN VEN TOR.

March 16, 1954 c. H. wURTz ETAL 2,672,020

TWO-TEMPERATURE REFRIGERATING APPARATUS Filed April 28, 1951 l1 Sheets-Sheet 6 ROOM TEMPERATURE SISO leo

PRESSURE bm 30o 2O 40 60 8O [O0 |20 |40 |60 |80 TEMPERATURE-DEGREES FAHRENHEIT 441/ muy March 16, 1954 c. H. wURTz ET A1. 2,672,020

TWO-TEMPERATURE REFRIGERATING APPARATUS AVERAGE FOOD COMP. TEMPERATURE u INV N TOR.

. H wil M 4' REfglglEERABNT CHARGE- OUNGES F-I2 W AVERAGE FROZEN FOOD TEMPERATURE :la o N .n m d March 16, 1954 c. H. wuRTz ET AL 2,672,020

Two-TEMPERATURE REFRIGERATING APPARATUS Filed Aprl 28, 1951 l1 Sheets-Sheet 8 FOOD OOMPARTMENT EVAPORATOR TEMPERATURE F.

TIME-HOURS I|O ROOM 20/A A423 qA /,1/\

FOOD COMPRTMENT EVAPORATOR TEMPERATUREV F. o 5

FOOD GOMPARTMEHT EVAPORATOR TEMPERATURE-E 2 TIME-HOURS 70 ROOM C7 /4 k INVENTOR.

fg www 'W6 SYSTEM BACK PRESSURE P Sl March 16, 1954 c. H. wuRTz ET AL 2,672,020

TWO TEMPERATURE REFRIGERATI NG APPARATUS HE DP ES UR B K RE SU I 2 3 4 5 6 7 "B19 I0 II I2 I3 I4 I5 I6 I7 I8 HOURS-90 ROOM SYSTEM BACK PRESSURE P.S.|.

SYSTEM HEAD PRESSURE RS I BAKPES R 0 5 6 7. 8 9 IO II HOURS-70 ROOM BY W' M im@ Ma INV N TOR.

March 16, 1954 C. H. WURTZ ETAL 2,672,020

Two-TEMPERATURE REFRIGERATING APPARATUS Filed April 28, 1951 l1 Sheets-Sheet l0 swf sea Marcl v16, 1954 c. H. wURTz ET AL Two-TEMPERATURE REFRIGERATING APPARATUS ll Sheets-Sheet ll Filed April 28, 195] ZKM Patented Mar. 16, 1954 TWO-TEMPERATURE REFRIGERATIN'G APPARATUS -Glifford ,-H.. Wurtz, Oakwood, .and James Jacobs, Dag/ton, hio, assigmors .to Gener-al MotorsCor-poration, Dayton, Ohio., a corporation of Delaware v .16 Claims.

This invention relates to refrigerating .appara- .ma :object of this :invention is (to provide an impmred mechanical refrigerator Awhich is adapted lto he manufactured in large quanti-ties and to be distribntedfand -used throughout the UnitedStates. lThis refrigerator is .refrigerated fby :a ysimple compressor, condenser, `evaporator system having no controls other than the usual rnfrigerasnt'expansion devi-ce and :a'fcompressor cycling control. The .refrigerator is provided `in its upper portion With a veryr low Atempera-tune frozen food compartment of rectangular cross adapted (to receive rectangular frozen food packages, to be fully packed with them, :and toprevent local warm spots among such frozen ffmdxpkwge- I Areinigerator is also .provided with an 11nfrozen food compartment 'to he maintained at "fa substantially .constant low temperamire, above 32 regardless of :the lfluctu-ati'ons in -enyironmenttemperatures. This unf-rozen food compartment is adapted to receive foods in large Quantities which zare te be maintained above 32 and are not likely to `'he dehydrated. The refrigerator 'also .isV provided a space within the Afood compartment inwh-ich :relatively .high humid-ities lare .maintained and in which foods may be preserved winch are likely .to otherwise .become dehydrated. Notwithstanding these advantages, the Arefrigerator is adapted .to operate satisfactorily in varying @atmospheric temperatures ranging from below 50 to as high aslllt is also adapted to =.operate `satisfactorily in yaryingdegrees-of atmospheric humidity, freonently .reaching .substantially the saturation point of 100% relative humidity, without Vdanger of accumulating -undesirabie `frrioistu-re Within the compartments o'rr within the insulation surthe compartments.

:this end, the cabinet provided with an outer is substantially :hermetically sealed throughout and is engaged by the door construction in a manner to reduce the infiltration of outside air into the refrigerator.

The frozen food compartment .is virtually surrounded on all except theV door side., 'with a freezing evaporator which is the first for initial stage of the 'prim-ary yevaporating system. This freezing evaporator is `r-.vlaced fon the outside yof the compartment, and the .inner side .of the compartment is made smooth to receive the Afrozen food packages and to abe easily scraped of a slight amount of frost which may gather after .lona 'periods of use. "..The construction is '2. such as to provide .a :large mass in heat exchange relation with the treezing evaporator. .'.Ihis oom- .partment is adapted to be maintained cold without defrosting for relatively v,long periods of time :(severfal months). Insulation ,is vplaced around the .frozen food compartment made of hermetically sealed bags of polyethylene containing glass or mineral Wool ewi-tlntlie surfaces :of the bags 'closely pressed against the jouter .surtace of the frozen food compartment thereby blocking the access of moisture to the freezing evaporator to such an extent that only :a .slight amount of frost can ever gather on the outer `suriace of the frozen food compartment (the .accumulation of which stops the early days of operation) and cannot :gather at all .inside :of the ibags.

The unfrozen food compartment is also ysurrounded .-by similar -bags of insulation pressed against the router surface of the compartment .so that .no .moisture Whatever can :gather inside the bags, and :substantial-ly no moisture can .gather on the outer Walls of the ufnfrozen food compartment. The lower .portion of V.the unfrozen food compartment may .be surrounded Aand contacted .by a refrigerant pan cooling evaporator which is closed circuit relationship with .a refrigerant condenser cooled .by .the pri mary refrigerant evaporating .system being -described. Thisspace, (in the lower part-of .the un- .frozen food compartment, tis .provided with one .or more covered, humidity retaining, food receiving pans or drawers adapted to vmaintain .a space .at relatively low temperature and Ahigh humidity for storing of green vegetables and the like. y

.In .order to cool the .major portion of Athe unfrozen ,food compartment, and in :order to ,prevent .the .accumulation of moisture either inside -of the unfrozen food compartment or in the insulation space, a frosting and defrosting evaporator of small mass and vholdover capacity is placed inside of the unfrozen food compartment and is preferably in the shape of `a vertical rectangular Iplate, in the upper rear part of lthe .u-nfrozen food compartment. This .frosting and de- .frosting levaporator constitutes the .second stage ofthe y:pri.-.-rriary evaporator circuit, since it is .in series refrigerant flow relationship with the freezing evaporator .surrounding the frozen .food compartment. The outer surface of the frosting and defrosting evaporator -is colder 'than the eater 'surface of the pa-n cooling evaporator and hence contirrmally freezes moisture .from the insulation space and prevents any material ac.i mimuiation; within fit.

A motor compressor unit and condenser are placed in the lower part of the refrigerator and are in refrigerant fiow relationship with the freezing evaporator and the frosting and defrosting evaporator. The compressor is cycled frequently (at least several times a day) to maintain the desired temperature conditions in the refrigerator and this is accomplished by providing a thermostatic switch having its thermostatic bulb in substantial contact with the frosting and defrosting evaporator. The switch starts the compressor when the frosting and defrosting evaporator reaches a temperature above 32 F., such as 36 F. insuring the defrosting of this evaporator. The compressor runs until this evaporator reaches a very low frosting temperature, lower than the temperature of the frozen food compartment, such as F. The construction and relationship of the freezing evaporator and the frosting and defrosting evaporator are such that a large portion. of the liquid refrigerant in the frosting and defrosting evaporator is forced, in liquid form, into the freezing evaporator at the beginning of the defrosting cycle, thus reducing the amount of heat and length of time required to defrost the frosting and defrosting evaporator.

This refrigerator is adapted to maintain the frozen food compartment uninterruptedly below 32 F. without defrosting for long periods of time, F

such as several months,l independently of the cycling of the motor compressor unit, which cycling occurs several times a day since the temperature of the liquid refrigerant in the freezing evaporator does not rise above 32 F. even during the defrosting periods. The refrigerator is maintained in proper condition by the automatic defrosting of the frosting and defrosting-evaporator, which operation is performed during each idle period of the compressor so quickly that no "'9 melting can take place in the frozen food compartment. The refrigerator can operate at very high efficiency in all sections of the country under varying conditions of atmospheric temperature and humidity without becoming frostor moisture bound either within its food preserving compartments or within its insulation space.

It is another object of our invention to provide a household refrigerator in which an above freezing food compartment is maintained at a substantially constant temperature and humidity by a primary evaporating means operating upon a defrosting cycle while adequate substantially constant sub-freezing conditions are maintained by a primary sub-freezing evaporating means.

Further obiects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings:

Fig. 1 is a vertical sectional view taken substantially along the line i-l of Figs. 4 and 5 of the upper portion of a two temperature refrigerator embodying one form of our invention;

Fig. 2 is a vertical sectional view taken substantially along the line 2-2 of Figs. 4 and 5 of the bottom portion of the two temperature refrigerator, the upper portion of which is shown in Fig. 1;

Fig. 3 is a diagrammatic view of the refrigerating system and its controls shown in full line with the outlines of the refrigerator cabinet shown in dot-dash lines;

Fig. 4 is a fragmentary front vertical sectional view taken substantially along the lines 4-4 of Figs. 1 and 2;

Fig. 5 is a fragmentary rear vertical sectional view 'taken substantially along the line 5-5 of Figs. 1 and 2 with the back insulation removed;

Fig, 6 is a view of the constant cut on type switch shown diagrammatically in Figs. 2, 4 and 5;

Fig. 7 is a fragmentary View of the switch shown in Fig. 6 showing the switch in the open circuit position;

Fig. 8 is a chart showing the total heat leak of the refrigerator cabinet and the heat leak for the separate compartments for various room temperatures;

Fig. 9 is a vapor pressure-temperature chart of the refrigerant used in the system;

Fig. 10 is a chart showing the ounces of refrigerant absorbed in the compressor lubricating oil under running conditions at various room temperatures and compressor dome pressures;

11 is a chart showing the effect of different amounts of refrigerant in the system upon the average food compartment temperatures and the average frozen food temperature in 90 and 110 F. room temperatures;

Fig. 12 is a chart showing typical cycling of the food compartment evaporator temperature in a 110 room;

Fig. 13 is a chart showing the typical cycling of the food compartment evaporator temperature in a room;

Fig. 14 is a chart showing the typical cycling `of the food compartment evaporator temperature in a 70 room;

Fig. 15 is a chart showing the typical cycling of the head pressure and back pressure under initial starting and subsequent normal running conditions in a room;

Fig. 16 is a chart showing the typical cycling of the head and back pressure under initial starting and subsequent normal running conditions in a 90 room;

Fig. 17 is a chart showing the typical cycling of the head pressure and back pressure under initial starting conditions and subsequent normal running conditions in a 70 room.

Fig. 18 is a diagrammatic view of a modified form of the invention in which there is provided a disengaging tank between the first stage primary freezing evaporator and the second stage primary refrigerating plate in the food compartment;

Fig. 19 is a diagrammatic view, similar to Fig. 18, in which the outlet of the refrigerated plate is connected directly to the suction inlet of the compressor;

Fig. 20 is a diagrammatic view vsomewhat similar to Fig. 19 in which the outlet of the refrigerated plate is connected to an accumulator located at a lower level in the insulation space and connected directly to thegsuction inlet of the compressor;

Fig. 21 is a diagrammatic view of a modified form of the invention in which the secondary condenser of the secondary refrigerating circuit is mounted in heat exchange relation with the accumulator which is located adjacent the freezing compartment in the insulation space; and

Fig. 22 is a diagrammatic view in which the secondary condenser of the secondary refrigerating circuit is mounted in heat exchange relation with an evaporator portion intermediate the first and second primary evaporator stages. j l

Referringnow to the drawings there is pro- 5 vided an. outer hermeticallyA sealing sheet. metal'. shell 2.0i enclosing the top. 22, bottom 24,v sides 2.5; and' 28,v and. rear 30: of4 the cabinet. The joints; or. this shelt are sealed. by' welding or other suite. able metal seal'I and preferably are additionally sealed'- on the; interior by the use. of some forno` ofnonsmetallic sealingy materiali such as asphalt: appliedin .molten form.A

There. is: provided a; freezing ccmpartlnentl 323 in the: upper portion ofthe cabinetin the form. of. a box1-shaped metal container having its front side, open.. This. freezing comparlament.v container 32s has itsl front edges connected; by a; member 34 of a thermoplastic material, called a breaker strip: or throat. to the front portion. 36 of the cuter shell. 2.11.- of the refrigerator.. Beneath the, freezing compartment container 32 there is pro-- vided.r a food.' compartment 38 in the form of. .a barella-pcd metal inner `container.' or liner having" itsiront Sidel Open.. The front edges of this. boxfshaped' container or liner 38., forming the fond'. compartment, are. connected by a, breaker- Strp ci* throat 4l!v of athermoplastic or other suit- A able.` poor heat. conducting material. with. the

front wall 36 of the outer shell `20..

A separate upper door 42 containing insulation is provided for the freezing compartment 32 and has arseal .44 of a suitable synthetic rubber whichV extends entirely around the door 42 to make sealing engagement with the front 3S of the outer cabinet shell 20, so that whenf the door 41 is closed the freezing compartment 32 is substantially scaled from the outside air. The lower compartment 38 is provided with a separate door 4.16 containing somewhat less insulation than the door 4 2. It. is likewise providedwith a sims ilar synthetic. rubber seal 48V extending entirely around the door which makes sealing engage-V ment with the fronty 360i the outer shell 20. This seals the food compartment 38 from the out.-v sidc. air. The sealing of the doors l2 and 46 against the front 35 of the outer shell` 2|) coin-` pletes the. hermetic sealing of the ,outside .of the cabinet .so that. no air or moisture can enter the cabinet except .by opening one of the doors..

The freezing compartment container 32 is provided with Smooth surfaced inner walls so that any snow or frost accumulated therein can be scraped or brushed off. When no melting occurs such snow or frost will not adhere firmly to the. freezing compartment container 32,.. freezing .compartment container 32 is cooled by the. firsty stage of a primary refrigerating system which includes a sealed motor compressor .unit 5D which delivers. compressed refrigerant to .a condenser 52, both of which are located in a machine compartment .|51 beneath. the bottom wall 2.4 .of the cabinet. 2.o. The motor compressor lmi 5l) is preferably .of the Side tvne vshown in the Rataiczak Patent No.. 2.377.935, issued June. 1.2, 1945., The unit -contains lubricant for lubricating the motor and compressor.. In such a motor compressor unit thecompressed refrigerE ant is delivered first to the superneat removing .Coil 5l which cools the mixture of compressed refrigerant and .oil vapor until the oil vapor is liquefied. The mixture is then delivered to the interior of the `shell of the motor compressor unit. liquefied oil remains in the interior of the shell but the compressed refrigerant in vapor form is delivered to the condenser 52.

The condenser 5.2 delivers liquid refrigerant through a capillary tube restrictor 54 to the inlet connection 5.5 oi.Y the tubular freezing. evape oratori which includes. a section of serpentine tubing 58 wound in serpentine fashion over the lil topi leftsideand bottom ci;y they freezing cetiniestk ment 32; after which there isa rentigeratedfloop]l on; extending through the back Wall of. the l partment 32 forwardy beneath. and.; in @Unmut with the bottom ofthe ice tray shelf 6.2' for n.110- viding fast freezing of ice in an icey trayshelf 62- is beneath4 another ice tray Shelf. 6.4? both. ofv which are supported upon the sidewall .anda bya vconnection 66 from 'the top of the freezing.

compartmenty container 32'. From the loop (i0 the,-

evaporator tubing extends in the form of a loop.. 68 upon the right side wall of the freezing. mmf pari-,ment 3.2. which ends in avertically rising Dor-` tion which assists in separating the liquid-:ree:- frigerant from its vapor. This connects directly to a portion 69: forming a trap for retaining liquid refrigerant in the tubular freezing evaporaton The tubular freezing evaporator and the con.-Y tainer 32 constitute a heavy mass of high hold: over capacity and is the rstor initial stage er section ofthe series type of' primary evaporating system.

The trap portion B9 is connected by a Smallbi; conduit l2 with the bottom of a vertical refrigs erated plate 90 spaced from, but. fastened to. the) rear wall of the food compartment container 3.8; within the food compartment. The refrigerated plate S has a minimum of mass and lowholdover capacity. It is provided with a. U-Shapd refrigerant passage 92 constituting .the` second stage or section of the series type. primary evapo` rator circuit. The passage. 9.2 extends across the bottom, up one edge,4 and backacross the-'ton of the plate 90. From the upper .end port-ion of the refrigerant passage S2 in the plate 9D there extends a refrigerant'condut 94 extending into thev top of a disengaging tankor accumulator 9E, extending substantially across` the; upper realedge of the freezing compartment. container 132 later 9B is adapted to trap. liquid refrigerantv and:V

for such refrigerant acts as the third' stage of the evaporating system. It is fas-tened by the. bracka. ets S8 to the adjacent. surface of the. container 32 so that it is in heat transfer relation therewith. The top. of this tank or accumulator 96 is connected by the refrigerant conduit f2 |y with a coupling |23 which connects with thev suction conduit |25 connecting directly with the inlet A.of the compressor in the motor compressor unit .51h

The bottom of the food compartment .38 is provided with two covered pans4 |21 .and |29 to` keep food aty -a high humidity. The covers of" these pans are conveniently arranged with a. slide.. able support for the pans so that the pans .can be pulled out as drawers. Since these paris |21,l and |29 are substantially closed 'by their covers, it is desirable. to provide additionalr .cooling so that the food within these pans is kept at a suitaable refrigerating temperature. For this purpose there is wrapped about the sides and 'backof the liner 38; in serpentine fashion, the tubing |3| which constitutes the evaporator of a seca ondary refrigerant circuit which includes .thev

seconda-ryl condenser condenses refrigerant at 2 a'suicient rate to evaporate refrigerant in the tubing |3l fast enough that the bottom portions of the liner 38 are kept at a temperature between about 34 and 36 F.

The operation of the refrigerating system is controlled by a thermostatic control switch 8B mounted on the inner side of the food compartment liner 33 as shown in Fig. 1. This switch 80 is shown in detail Figs. 6 and l and includes a U-shaped metal frame 323 having a switch block 322 of a suitable electric insulating material mounted between the open ends thereof. Within the U-shaped frame 32s there is provided a metal bellows 324 adjustably mounted by the adjustable mounting screw 326 threaded through the yoke of the frame 323. The bellows 324 is connected by a metal follower 323 and a link 333 of an electrical insulating material with the leaf spring contact member 332. One end of this leaf spring contact member 332 is anchored to an electric terminal 334 extending through the block 322. The other end of the leaf spring 332 is provided with an electrical contact which is adapted to make and break contact with the adjustable terminal 33t` provided with an electric Contact on its inner end. The bellows 324 is therefore directly connected with the leaf spring member 332.

To insure snap action operation of the spring contact member 332, the bellows follower 323 has pivotally connected to it, the inner ends of the pair of triangular-shaped toggle links 338 and 343. The outer end of the link 343 is pivotally connected to the cantilever end portion of a bartype spring 342. The lower end of the bar-type spring is loosely anchored in an aperture in the yoke of the frame 320 as is clearly shown in Fig. 6. At an intermediate portion, the bar-type spring 3,412 is engaged by a screw 343:3 which is threaded through the side of the frame 32S. After this screw 344 is properly adjusted to apply the proper normal column loading to the toggle links 338 and 343 to insure the snap action desired, it locked in place by some form of sealing material designated by the reference characters 343.

The bellows follower 328 is provided with a projection 338 which operates between the upper projection 35B and the lower projection 352 upon an adjusting screw, threaded through the block 332. This screw is adjusted so that the lower projection 352 stops the opening movement of the leaf spring contact member 332 at the point.

where the toggle links 333 and 343 are exactly in alignment as shown in Fig. '7. This adjustment insures that the switch will always have a constant closing temperature after the adjusting screw 325 is properly set. According to this invention, the screw 323 may be adjusted so that the closing temperature of the switch is from 34 to 36 F. We prefer to set the switch to close at 36 F.

The switch, however, is provided with a manually adjustable switch opening control. This may take any desirable form but as one example, we have shown a screw 351i provided with a very fine thread which is threaded through an aperture in the side wall of the frame 320. This screw is provided with a bearing which carries a bearing support for the outer end of the toggle link 338. The screw 354 is provided with gear teeth 356 which are in engagement with a pinion 35S fixed to the pinion shaft 363. The opposite end of this pinion shaft 333 extends through the hollow interior of the screw 3114Y which serves as a bearing and has a knob 362 fastened to the opposite end. This knob 362 may be turned to rotate the screw 353 so as to vary the column loading upon the toggle links 338 and 343. This arrangement may be adjusted to provide a cut off point which varies between about plus 5 to minus 10 F. The shaft 333 is also provided with a cam 363 adapted to engage a projection 336 upon the bellows follower 328 for the purpose of forcibly holding the leaf spring member 332 in the open circuit position. The bellows 324 is connected to a capillary tube 368, the end 310 of which is formed into a serpentine shape and clamped 'to the back of the refrigerated plate 33 as shown in Figs. l, 4 and 5.

This arrangement insures that the refrigerated plate will be cooled to a low temperature of about plus 5 F. to minus 10 F. during every running cycle but after reaching this point, the operation of the system will be stopped and the refrigerated plate 93 will rapidly warm up to a temperature above 32 F., such as 36o F. so that it will completely defrost during every idle period. However, because of the relatively high mass of the freezing compartment container and its first stage evaporating means, the packages within the freezing compartment container and the container itself will remain at low freezing temperatures such as 12 F. or below, despite the defrosting of the second stage evaporator during the idle period. The operation of the plate 90 under such a wide cycle keeps the humidity in the compartment 33 well below the saturation point so that food that is placed within the compartment 3s will not become wet. However, foods which are subject to dehydration should be kept in the pans l2? and 123. Foods in closed containers which are not subject to dehydration are placed in the remainder of the food compartment 38.

While it is possible to seal the outer cabinet shell 23 from the air in the room, because of construction problems, it is not possible to seal the insulation space from the interior of the freezing compartment container 32 and the food compartment liner 33. It is wel] known that moisture vapor tends to migrate to the coldest point to which it has access. To prevent this moisture Vapor from migrating to the freezing compartment container 32 the freezing compartment container 32 is sealed from the food compartment liner 38 by having a separate door 42 with its own seal 43. The moisture vapor is prevented from migrating to the outer surface of freezing compartment container 32 by being surrounded with insulation in the form of glass or mineral wool enclosed in hermetically sealed bags of a suitable plastic material such as polyethylene or polyvinylidene chloride.

For example, there is provided a bag M1 in the space above the freezing compartment container 32 and the bags |43 and l5! in the insulation spaces at the side of the container 32 and a bag I5! between a catch pan IM and the top of the food compartment liner 38. There is also provided a bag which fills the insulation space at the rear wall of the cabinet. All these bags closely envelop the freezing compartment container 32 and the evaporator tubing surrounding it. The material forming the bags is very flexible and resilient and the glass or mineral wool used inside these bags is likewise very flexible and resilient so that the bags hug and surround the container 32 and the first stage primary evaporator very closely so that access by moisture Vapor to these surfaces through the insulation space is almost completely blocked so that substantially no moisture is deposited thereon.

The moisture vapor therefore within the outer shell 2o migrates to the next coldest spot to ywhich it has access. .'Ihe next coldest spot is the refrigerated lfplate 9i) which may be cooled to as .lowl as #minus 18 F. `during the .running royale. This causes 'any moisture vapor within the `insulation .spaces to Vtend, to .migrate to lthe yrefrigei'ated plate 90 and -to be deposited as .frost `lrthereon. This keeps :the insulation dry. ISince evaporator plate si is colder than the evap- -orator |31 on the outer surface of the .liner 38, 'fthe evaporator |31 Vwill beprevented from -con- -densing moisture in the insulation space.

.Because the switched is set to prevent the start-ing oi 'the refrigerating system until the ,reltrigerating Aplate Fes :reaches Athe 'temperature vof Sfrom 314'to 3`6` the refrigerating plate H0 will defrost :during leach idie .period of the motor -icompressor cunit. .The vdefrost avater lWill fall lto VAthe 'bottomof the 1liner t3i. and will be conducted .thy :fthe Adrain zlf'i ztoea .pan |59 fin the .machine compartment. 1

Occasionally .it imay be desired to :completely defrost the interior pf the .freezing compartment container .or it may :be desired to shut down the rc'fri'gerratingsystem :for moving it to another vlocation, orsorne other reason. For thispurpose fthere is'provided an 'outlet |62 in theibottom of the freezing-compartment"container A32 .for drainingffthie defrost Water :therefrom into the catch pan 41|. Should lthere :nbefany Vfrost on .the outiside fof `the container .32 and the rst stage .fpri- /mary-evaporator,ithedefrost water therefrom will llikewiseloefcollectedxby the Voatchpan 41| since the 'ea-tch pan ilrl fprotrudes beyond the periphery of ftheiIreezing-rcorrtainer 82. .Thecatch pan etti-lv slopes Atolthe.rightside offthecabinet and :is-provided with 1a 1drain :outlet |4`3 which 'extends through .an l'aperture into the `:top vvall :of :the food 'compartnie'rit diner 38. Uponxthebottomfside Y'of thetop fwallaof the `liner E3B zthe -drain loutlet :|43 is proivide'd with f a spout M5 Vfor 4discharging the defrost .Water-ion `to the right @vertical .side -wall of theifood Icompartment :liner r3 8. This fvvater ovvs @dov/.nahe side rysallto thebottomaof Sthelinerand is =.deposited in the zpan |59 .in fthe same rway :as `vtheitlefroslrwater1fromzthe platee.

` .=If dzhezrefrigerating system Were-f-charged-with veinormal.ifu'll amount of :refrigerant there `would te a ftend'encyto 'overly .cool .the uunfrocen :food compartment .its in .a relatively :cold :room vsuch its ll70 iffhis is -iprevented `by Yhaving a :lesser `amount ofretrigerantin the ;primary :refrigeratinigsys'temathansis customary. .According-.toom .invention We :use fa 'refrigerant such as :diuoro- -fdiuhloromethaneiwhichis,absorbedinandaevolved -i'rom -fthe :lubricant iin athe Asystem :as A.rsh'otvn Eig .'10, :Manyothenrefrigerantshave this propkerty. The totalrrefrigerantpharge providedin the-system:approximately .equal in volume Lto 'attra-amount ofxrefrigerant required tooompletely -fiillfthe Aiirst stage ^'primary evaporator, that Iis V.the Atubular lfreezing fevaporator mounted .upan the freezing container 32', ...plus xthe tamountsof @refrigerant absorbed bythe lubricatingzoiliinithe :motor compressor :unit Iduring :running pondi- .tionsinLa 70:room. .By :using .a refrigerant which lis 2 readily :absorbed -in the lubricant .used and providing sufficient lubricant in .the V.systeI-n .on the? high-side inthe motorl chamber.- oiathersealed .unit 59,1there-is provided .an yinherent adjusting :factor `because :at -warmer :room -temperatures :there-is less refrigerant .absorbed in .thellubriscant providing .aerea-ter amounts sof refrigerant food compartment.

for supp-ly .to .the yrefrigerated plate 9|! during running conditions so that an additional .amount of refrigeration is .provided .for .the food compartment .at the warmer room .temperatures .to .compensate for .an increase in heat leak into the This .provides a .system in which .the A.average .temperatures in the ioodcompartment .'38, which .are relatively critical, may be maintained vat very nearly the .same temperav.tu-re .regardless .of .changes y.in .the room temperature .in which V.the refrigerator is located. ,At the same time, the .frozen food .compartment .3.8 .is vkept .at `safe refrigeration temperatures. YIii-.iis ,permissible for .the .temperatures in `the frozen vfood Acompartment .32 to vary ymore than 4the .temperatures .in .the .unfrozen food compartment T38.

The ,providing of the accumulator 96 vfollowing the refrigerated yplate in the .primary refrigerant vcircuitaids in providing just the proper .amount `of refrigerant vfor .the .different compartments -.to maintain .the desired .temperatures -under varying .room temperature conditions. .To a .limited extent :it yacts .as .a `third .stage ,evap- .orator .and .under very Warm room ,temperature conditions can .receive ,unevaporated .liquid .reirigerant .trom the .refrigerated plate during .running conditions. Thisaccumulator preventssuch refrigerant from entering .the suction `.conduit |125. .Immediately after the termination .of .the Arunning period, the .evaporation .of .the .refrigerant .within the plate .9.0 .will cause .the vapor .pressure therein to rise. .During the 4:cunning Aperiod .the rststage ofthe primary evaporating system Awhich .is in `contact with .the .outside vof the freezing compartment Acontainer 3.2 .conducts considerable iamounts Iof refrigerant .vapor in addition y.to `the liquid refrigerant. The` proportion .of vapor to liquid .increases gas the .refrigerant ,progresses through the tubing.

Consequently `when .the motor-compressor `unit .50 visstopped Vbythe refrigerated plate .9,9 reaching the predetermined low ltemperature .to `Which .the vcontrol .switch 3.0 set, `vthere .is .a consider- .able vapor space in .the latter portion .of vthe .rst.stagevcvaporaton Since vthe .food compartment 38 .is .much -Warmer rthan .the freezing. compartment .'32 .the vapor pressure will ybe much V.higher `Within `-the refrigerated plate .90 which .constitutes thefsecond .stage primary evaporator. .The vapor vpressima within the plate .90 VWill rise .much morerapidly .becauseiof lits relatively small .mass land -large surface Varea .which ithas exposed A.to the atmosphere in the lfood 'compartment-.38 which isatatemperature of. about 35F. .as .illustrated in Fig. The Iirst stage yfreez- .in'gcompartment evaporator which surroundsthe container 32 is apartof-afrelativelyheavysmass rheld .at a :relatively .low temperature .as illustrated zinzFig. 111 s so :that rthe vapor temperature .rise fwiil be :very slow as ycompared to `the :vapor ipressnre 'rise I' in lthe refrigerant `plate V'81). This 4Will cause the liquid fin -ft'he refrigerated `plate "Bil and the 'endof the running cycle Yto `-be forced lin the reverse ydirection upwardly lthrough the `pipe A"l2 and `over "the trap portion 69 `loaclrir1`1zo thefloop'portione' `of the rst stage evaporator .until the plate 'Spl vis Tsubstantially A,completely stripped v.of .liquid refrigerant. .Any "liquid .refr'igerant in .the refrigeratedtplate 99 Whicnhappensto .escape this ...liquid :returning action will be `:prickly .evaporated .and .condensed in the r.ac-

cumulator .tank ',945 .which because l of its A:location .andicormectionris yflreptj. .e .t :temperatures near the temperature of the freezing compartment container 32.

This novel system provides for the rapid defrosting of the refrigerated plate 90, thereby shortening the idle period of the refrigerating system under all room temperatures. It keeps the average box temperature under all conditions relatively low in all room temperatures and yet insures complete defrosting of the refrigerated plate 90 during every idle period of the motor compressor unit 50. By keeping the idle period `.relatively short under all room temperatures.

the freezing compartment 32 is maintained at safe refrigerating temperatures for frozen foods under varying room temperature conditions.

To adjust the system to provide the proper relationship of temperatures maintained in the freezing compartment and in the food compart- `ment, the system is placed in a 110 room and after reaching uniform operating conditions, the opening or cut oif point of the thermostatic switch 80 is adjusted by adjusting the adjusting screw 326 until the desired temperature is attained in the freezing compartment 32. In general, this point may be adjusted between minus 15 and plus 5 F. to obtain a package temperature below 10 F. The refrigerator is then placed in a 70 room and operated until it reaches a substantially uniform condition. The refrigerated plate should not receive substantial amounts of liquid refrigerant during the initial portion of the running cycle. If substantiai amounts of liquid refrigerant is received during the initial portion of the running period or if the compartment 33 is too cold, there is too much refrigerant in the system and refrigerant should be removed from the refrigerant circuit until desired food compartment temperatures are obtained. By this arrangement desirable refrigerating temperatures in both the freezing compartment 32 and the food compartment 33 are maintained under all room temperatures varying between 70 and 110 F.

As one specific example of this invention, the refrigerator may be arranged to provide the freezing compartment 32 with 2 cu. ft. of interior space and the food compartment 33 with 8 cu. ft. of space. The liner 38 has a surface area of about 3690 sq. in. The total surface area of the refrigerated plate 90 is about 40S square inches so that the refrigerated plate 90 has a surface area of about 1li) of the total surface area of the food compartment liner 38. The cabinet has a heat leak rate shown by the chart of Fig. 8. A e hp. sealed motor compressor unit is provided. The compressor has a displacement of 0.75 cu. in. per revolution and operates at a speed varying from 1750 R. P. M. to 1700 R. P. M. as the suction pressure varies from 0 lbs. gauge to 21 lbs. per square inch gauge. The compressor has a nominal capacity of 565 B. t. u. per hour at 0 lbs. gauge and 1179 B. t. u. per hour at 21 lbs. gauge.

The suction line connected directly to the compressor intake and the compressor 49 then discharges into the super-heat removing coil 5i where the lubricant is condensed out of the refrigerant vapor and the mixture is returned to the interior of the shell of the sealed motor compressor unit 50 where the lubricant is collected while the refrigerant vapor is conducted to the condenser 52. The system is charged with l5 ounces of 525 viscosity mineral oil lubricant.

The condenser 52 has a capacity ample to condense the refrigerant vapor to liquid more rapidly than the liquid refrigerant flows out of the conous room temperatures.

denser 52 through the restrictor 54. The restrictor 5e has a length of about 120 inches and an interior diameter of 0.031 inch. The first stage of evaporator tubing, which is in direct thermal contact with the freezing compartment container 32, is about 34 feet long and has a volume of about 34 cu. in. The refrigerant passage 92 in the refrigerant plate has a length of about 49 inches and a volume of about 2 cu. in. The system is charged with approximately 39 ounces of difluorodichloromethane (F1-12) having a volume in liquid form of about 49 cu. in. If desired, about 2 c. c. of methol alcohol having a volume of only 0.12 cu. in. may be added to the refrigerant in the system to prevent freezing in the restrictor 54 if the system is not completely dry. The accumulator 03 is about 20 vinches long and has an outer diameter of about 11/2 inches and a total volume of about 321/2 cu. in. As illustrated by the chart, Fig. 10, there is about 101/2 ounces absorbed in the oil under running conditions in a 70 room. This corresponds to a liquid volume of about 13 cu. in.

The liquid volume of the free refrigerant in the system in a 70 room therefore is 49 minus 13 or 36 cu. in. This is substantially equal to the total volume of rst stage freezing evaporator which has a volume of about 34 cu. in. The effect of varying the charge of refrigerant in the system is shown in the chart of Fig. 1l for 70, 90 and 110 room temperatures. With a refrigerant charge of 39 ounces, the average food compartment temperature is about 35 F. with a total average variation of less than 1 F. in vari- To our knowledge, no previous refrigerator of this or any similar multitemperature type can approach such a performance. The frozen food compartment temperature varies from about 0 to 6 F. which is quite satisfactory. As shown by the chart, further reduction in the refrigerant charge lowers the average frozen food temperature and causes a slight widening of the temperature limits in the unfrozen food compartment 33. Reducing the refrigerant charge also increases the percentage of running time and slightly increases the amount of current consumed. While the exact figures given in the foregoing example need not be strictly adhered to but the various proportions are material and reasonable adherence to the proportions indicated are necessary to achieve the splendid performance reported above.

The manner in Which the substantially uniform unfrozen food compartment temperature is achieved is illustrated in the charts, Figs. l2 to 14. In Fig. 12 in a 110 room the off period time is shown to be about a half an hour. During this period, the temperatures of the refrigerator plate 90, which is shown in full lines in the chart, rises rapidly from minus 10 F. to a temperature of 32 F. It remains at this temperature during the time the frost melts therefrom and as soon as the frost is melted, rises rapidly to the cut on or switchclosing temperature of the switch illustrated as being 34 F.

During this idle period, because there is no liquid refrigerant within the refrigerated plate 90, the vapor pressure in the refrigerating system does not correspond to the temperature of the refrigerated plate. To illustrate this, there is shown a dotted line 425 which indicates the temperature corresponding to the refrigerant pressure prevailing in the system during the idle and operating periods. It will be seen that this rises to only a pressure corresponding to about 11 liquid refrigerant from the refrigerated plate 92 during the idle periods of the motor compressor unit 50.

In Fig. 19 there is shown another modification in which similar parts likewise bear the saine rele erence characters as in the previously described forms and the description thereof likewise applies. This form shown in Fig. 19 differs from Fig. 18 in that the refrigerated plate 5c@ is provided with a serpentinevshaped refrigerant passage 592 which connects directly with the bottom of an accumulator' space 526 formed directly in the refrigerated plate 99. The accumulator space 596 also differs from the accumulator 96 in that the inlet connection is made at the bottom of the space and the suction outlet thereof is connected at the end thereof by a suction line 525 which connects to the inlet of the motor compressor unit 50. In both of these forms, many of the details, such as the pans |21 and |29 as well as the secondary circuit which cools them, have been omitted. All of these details however can be included in the forms shown in Figs. 18 and 19 in substantially the same arrangement.

In this system, the construction is simplified because the separate connection between the refrigerated plate t and the accumulator 96 is omitted. During the idle period, the refrigerant in the refrigerated plate .E90 is returned through the connecting conduits 'i2 to the disengaging tank 569 by the vapor pressure above the surface of the liquid refrigerant in the passage 522. This assures operation of the refrigerating system lin substantially the same manner as explained in connection with Figs. 1 to 17. flowever, it is more difficult to adjustk this system to maintain as low temperatures in the freezing compartment container 32 as are attained with the forms shown in Figs. 1 to 18. The reason for this appears to be that the accumulator 9S considerably assists in the cooling of the container 32.

In Fig. there is shown diagrammatically another modification in which similar parts are designated by the same reference characters and function in the same manner as explained in the previous modifications. In this modication, there is provided a secondary condenser 62| which is clamped to the portion of the tubular primary freezing evaporator between the right i side portion B8 and the trap portion 69. The evaporating portion 623 is wrapped around the lower exterior of the liner 38 for cooling the high humidity pans |21 and |22. Liquid refrigerant is fed to the evaporator 623 from the condenser 62| through the supply conduit $22 while the evaporated refrigerant from the secondary evaporator B23 returns to the condenser 62| through the return conduit 621.

Fig. 21 shows another modication in which some of the parts bear the same reference characters and operate in the same manner. Fig. 21 differs from previous forms in that the evaporating portion 123 which is wound about the lower exterior portion of the liner 38 is connected to a secondary condenser 12| which is located in heat exchange relation with the accumulator 96 located in the insulation space adjacent the freezing compartment container 32. The bottom of the condenser 12| is connected to the supply oonduit 126 which connects to the bottom of the evaporator 123 while the top of the evaporator 123 is connected by the return conduit 121 to another portion of the condenser 12|.

In Fig. 22, there is shown still another modi flcation in which the same bear the same reference characters as in previous modifications and operate similarly. ln this particular form, the lower portion of the passage 92 in the refrigerated plate 91| is connected by a refrigerant supply conduit 825 to an accumulator 895 which is located Within the insulation space 828 between the back wall of the food compartment liner 38 and the back wall of the outer shell 20. The refrigerated plate 2t is thereby prevented from accumulating liquid refrigerant thereby speeding defrosting during the idle period. The top of this accumulator 895 is connected directly to the suction conduit |25 connecting to the inlet of the motor compressor unit 50.

The bottom of the liner 38 is cooled by a secondary refrigerant evaporator 828 which is wound about the lower exterior portion of the liner 38 for cooling the high humidity pans |21 and |29. The top of this evaporator 823 is connected by the conduit 821 to the upper portion of a secondary refrigerant condenser 82| which is mounted in heat exchange relation with the accumulator 893. This condenser 82| evaporates liquid refrigerant reaching the accumulator 896. The bottom portion of the condenser 82| is connected by a liquid supply conduit 825 with the lower portion of the evaporator 823.

In Fig. 20, the secondary condenser 62| tends to heat the refrigerant leaving the tubular freezing evaporator so as to reduce the amount of liquid refrigerant supplied to the passage 92 in the refrigerated plate 90. In Fig. 21 the secondary condenser 12| evaporates any liquid refrigerant which may collect in the accumulator 96. In Fig. 22 the secondary condenser 82| evaporates the refrigerant which may collect in the accumulator 89e. In each of these three modifications, the secondary circuit is used to prevent excess amounts of liquid refrigerant from flowing farther through the refrigerant circuit than is desired.

In accordance with the provisions of rule 78a, reference is made to the following prior led application: S. N. 193,963 filed November 3, 1950.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, as may come within the scope of the claims which follow.

What is claimed is as follows:

1. Refrigerating apparatus comprising: a cabinet; a cycling refrigerant liquefying means in said cabinet; a frozen food compartment in said cabinet to be maintained substantially below 32 F. and adapted to be maintained uninterruptedly below 32 F. without defrosting for long periods Aof time, such as several months, independently of the cycling of said refrigerant liquefying means; an unfrozen food compartment to be maintained substantially above 32 F. in said cabinet; insulation for said compartment including a substantial heat transfer barrier between said compartments; a freezing evaporator in heat exchange with said frozen food compartment; a frosting and defrosting evaporator inside said unfrozen food compartment; refrigerant flow connections providing a circuitous series connection from said refrigerant liquefying means first to said freezing evaporator, thence to said frosting and defrosting evaporator, thence back to said refrigerant liquefying means; the refrigerant connections between the freezing evaporator and the frosting and defrosting evaporator being open and substantially unrestricted, and a thermostatic cycling control having a thermally sensitive element in direct intimate contact with said frosting and defrosting evaporator and having cycling means for starting and stopping said liquefying means, respectively when the temperature of said frosting and defrosting evaporator rises above 32 F. and when it falls below the temperature to be maintained in said frozen food compartment; the combined holdover capacity of said frozen food compartment and said freezing evaporators being sufficiently great in relation to the holdover capacity of said frosting and defrosting evaporator to prevent the temperature of said frozen food compartment from rising above 32 F.

2. Refrigerating ap-paratus comprising: a cabinet; a cycling refrigerant liquefying means in said cabinet; a frozen food compartment in said cabinet to be maintained substantially below 32 F. and adapted to be maintained uninterrup-tedly below 32 F. without defrosting for long periods of time, such as several months, independently of the cycling of said refrigerant liquefying means; an individual door for said compartment; an unfrozen food compartment to be maintained substantially above 32 F. in said cabinet; insulation for said compartment includingr a substantial heat transfer barrier between said compartments; a freezing evaporator in heat exchange with said frozen food compartment; a frosting and defrosting evaporator inside said unfrozen food compartment; refrigerant iiow connections providing a circuitous series -connection from said refrigerant liquefying means rst to said freezing evaporator, thence to said frosting and defrosting evaporator, thence back to said refrigerant liquefying means; the refrigerant connections .between the freezing evaporator and the frosting and defrosting evaporator being open and substantially unrestricted, said refrigerant ow connections being constructed to cause `liquid refrigerant to be forced by partial evaporation of refrigerant at the start of a defrosting operation from said frosting and defrosting evaporator to said freezing evaporator.

3. Refrigerating apparatus comprising: a cabinet including an outer hermetically sealed casing; a motor compressor unit and a condenser in said cabinet; a frozen food compartment in said cabinet to be maintained substantially below F. without defrosting for long periods of time, such as several months, independently of the cycling of said motor compressor unit; an unfrozen food compartment to be maintained substantially above 32 F. below said frozen food compartment; insulation inside said outer casing and 4outside and between said compartments, with breathing openings or `accesses to said unfrozen food compartment; a freezing evaporator outside and in contact with all of -the'walls of said frozen food compartment except the door opening; a frosting and defrosting evaporator inside said unfrozen food compartment; refrigerant flow and heat exchange connections between said evaporators and said motor compressor unit and condenser; the refrigerant connections between the freezing evaporator and the frosting and defrosting evaporator being open and substantially unrestricted, and a thermostatic switch controlling the cycling of said motor compressor unit and having a thermostatic bulb in close thermal contact with said frosting and defrosting evaporator, set to start said motor compressor unit when the temperature of said frosting and defrosting evaporator rises above 32 F. and to stop said motor compressor unit when the temperature of said 18 frosting and defrosting evaporator falls below the temperature to be maintained in said frozen food compartment.

4. Refrigerating apparatus including an above freezing food compartment and a below freezing compartment, a thermal heat transfer barrier between said compartments, a refrigerant liquefying means, a freezing evaporating means in heat exchange relation with said below freezing compartment and having its inlet connected to an outlet of said liquefying means, a food compartment evaporating means in heat exchange relation with said food compartment and having its inlet connected to an outlet of said freezing evaporating means, the refrigerant connection between said freezing and food compartment evaporating means being open and substantially unrestricted for refrigerant ow, means for returning evaporated refrigerant from said freezing and food compartment evaporating means to said liquefying means, and thermostatic cycling control means having a thermally sensitive element in direct intimate contact with said food compartment evaporating means having means for preventing the starting of said liquefying means until the food compartment evaporating means reaches a temperature above 32 F. for defrosting said food compartment evaporating means and having means for preventing the stopping of said liquefying means until said food compartment evaporating means is cooled to below freezing temperatures.

5. Refrigerating apparatus including an above freezing food compartment and a below freezing compartment, a thermal heat transfer barrier between said compartments, a refrigerant liquefying means, a freezing evaporating means in heat exchange relation with said .below freezing compartment and having its inlet connected to an outlet of said liquefying means, a food compartment evaporating means in heat exchange relation with said food compartment and having its inlet connected to an outlet of said freezing evaporating means, the refrigerant connection between said freezing and food compartment evaporating means being open and substantially yunrestricted for refrigerant flow, means for returning evaporated refrigerant from said freezing and food compartment evaporating means to said liquefying means, and thermostatic cycling control means having a thermally sensitive element in directL intimate contact with said food compartment evaporating means having means for preventing the starting of said liquefying means until the food compartment evaporating means reaches a temperature above 32 F. for defrosting said food compartment evaporating means and having means for preventing the stopping of said liquefying means until said food compartment evaporating means is cooled to below freezing temperatures, said belowfreezing compartment having a sufficiently slower heat leak than said food compartment and said freezing evaporating means having sufficiently greater mass relative to said heat leak than said food compartment evaporating means that said below freezing compartment is maintained at substantially constant sub-freezing temperatures during the cycling of said liquefying means.

6. Refrigerating apparatus including an above freezing food `compartment and a below freezing compartment, a thermal heat transfer barrier between said compartments, a refrigerant liquefying means, a freezing evaporating means in heat exchange relation with said below freezing 

